1. Field of Invention
The present invention relates to a process for producing omega-9 highly unsaturated fatty acid and lipid containing the same by fermentation using a mutant strain in which xcex9412 desaturation activity has been decreased or lost, but at least one of xcex945 desaturation activity, xcex946 desaturation activity and chain length elongation activity is elevated.
2. Related Art
Omega-9 highly unsaturated fatty acids, such as 5,8,11-eicosatrienoic acid (referred to as mead acid) and 8,11-eicosadienoic acid, are known to exist as one of the constituent fatty acids of animal tissue that has become deficient in essential fatty acids. However, it has been extremely difficult to isolate and purify them since they are present in extremely small amounts. Since it is possible for these highly unsaturated fatty acids to become precursors of the leucotriene 3 group in the body, considerable expectations have been placed on their physiological activity. Their use for anti-inflammatory, anti-allergic and anti-rheumatic effects has recently been reported (Japanese Unexamined Patent Publication No. 7-41421).
There is therefore a strong desire to develop a method for producing omega-9 highly unsaturated fatty acids in large amounts. A process for producing omega-9 highly unsaturated fatty acid and lipid containing the same was previously completed by performing mutation on microorganisms having the ability to produce arachidonic acid and isolating those microorganisms in which xcex9412 desaturation activity has been decreased or lost (Japanese Unexamined Patent Publication No. 5-91888). However, although it is revolutionary and significant that a process for producing omega-9 highly unsaturated fatty acid and lipid containing the same was developed since such a process had not existed in the past, there was still much room for improvement in yield. Consequently, there has been a strong desire to develop a process for efficiently producing a larger amount of omega-9 highly unsaturated fatty acids.
Thus, the present invention is intended to provide a process that makes it possible to produce omega-9 highly unsaturated fatty acid or lipid containing the same in a large amount using conventional inexpensive media.
As a result of various researches conducted to achieve the above-mentioned object, the inventors of the present invention found a mutant in which xcex9412 desaturation activity has been decreased or lost, but at least one of xcex945 desaturation activity, xcex946 desaturation activity and chain length elongation activity has been elevated, thereby leading to completion of the present invention.
Thus, the present invention provides a process for producing lipid containing omega-9 highly unsaturated fatty acid comprising the steps of:
culturing in a medium a mutant strain obtained by mutation on a microorganism having an ability to produce arachidonic acid belonging to a genus selected from the group consisting of the genera Mortierella, Conidiobolus, Pythium, Phytophthora, Penicillium, Cladosporium, Mucor, Fusarium, Aspergillus, Rhodotorula, Entomophthora, Echinosporangium and Saprolegnia, in which xcex9412 desaturation activity has been decreased or lost, but at least one of xcex945 desaturation activity, xcex946 desaturation activity and chain length elongation activity has been elevated; and,
recovering lipid containing omega-9 highly unsaturated fatty acid from the culture.
Moreover, the present invention provides a process for producing an omega-9 highly unsaturated fatty acid comprising the step of recovering the omega-9 highly unsaturated fatty acid from the culture or lipid obtained according to the process described above.